From 3ac88a9948792b092a4b11323e2abd1ecbe0cc68 Mon Sep 17 00:00:00 2001 From: Alexandre Courbot Date: Tue, 24 Feb 2026 11:25:34 +0900 Subject: rust: str: make NullTerminatedFormatter public If `CONFIG_BLOCK` is disabled, the following warnings are displayed during build: warning: struct `NullTerminatedFormatter` is never constructed --> ../rust/kernel/str.rs:667:19 | 667 | pub(crate) struct NullTerminatedFormatter<'a> { | ^^^^^^^^^^^^^^^^^^^^^^^ | = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default warning: associated function `new` is never used --> ../rust/kernel/str.rs:673:19 | 671 | impl<'a> NullTerminatedFormatter<'a> { | ------------------------------------ associated function in this implementation 672 | /// Create a new [`Self`] instance. 673 | pub(crate) fn new(buffer: &'a mut [u8]) -> Option> { Fix them by making `NullTerminatedFormatter` public, as it could be useful for drivers anyway. Fixes: cdde7a1951ff ("rust: str: introduce `NullTerminatedFormatter`") Signed-off-by: Alexandre Courbot Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260224-nullterminatedformatter-v1-1-5bef7b9b3d4c@nvidia.com Signed-off-by: Miguel Ojeda --- rust/kernel/str.rs | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'rust/kernel') diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs index fa87779d2253..3f8918764640 100644 --- a/rust/kernel/str.rs +++ b/rust/kernel/str.rs @@ -664,13 +664,13 @@ impl fmt::Write for Formatter<'_> { /// /// * The first byte of `buffer` is always zero. /// * The length of `buffer` is at least 1. -pub(crate) struct NullTerminatedFormatter<'a> { +pub struct NullTerminatedFormatter<'a> { buffer: &'a mut [u8], } impl<'a> NullTerminatedFormatter<'a> { /// Create a new [`Self`] instance. - pub(crate) fn new(buffer: &'a mut [u8]) -> Option> { + pub fn new(buffer: &'a mut [u8]) -> Option> { *(buffer.first_mut()?) = 0; // INVARIANT: -- cgit v1.2.3 From 08da98f18f4f99aa16838397b76086d2d1d364b3 Mon Sep 17 00:00:00 2001 From: Gary Guo Date: Mon, 2 Mar 2026 16:42:34 +0000 Subject: rust: ptr: add `KnownSize` trait to support DST size info extraction Add a `KnownSize` trait which is used obtain a size from a raw pointer's metadata. This makes it possible to obtain size information on a raw slice pointer. This is similar to Rust `core::mem::size_of_val_raw` which is not yet stable. Signed-off-by: Gary Guo Reviewed-by: Benno Lossin Acked-by: Miguel Ojeda Link: https://patch.msgid.link/20260302164239.284084-2-gary@kernel.org [ Fix wording in doc-comment. - Danilo ] Signed-off-by: Danilo Krummrich --- rust/kernel/lib.rs | 1 + rust/kernel/ptr.rs | 27 ++++++++++++++++++++++++++- 2 files changed, 27 insertions(+), 1 deletion(-) (limited to 'rust/kernel') diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 3da92f18f4ee..510cc7fe4961 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -20,6 +20,7 @@ #![feature(generic_nonzero)] #![feature(inline_const)] #![feature(pointer_is_aligned)] +#![feature(slice_ptr_len)] // // Stable since Rust 1.80.0. #![feature(slice_flatten)] diff --git a/rust/kernel/ptr.rs b/rust/kernel/ptr.rs index 5b6a382637fe..e91de5f0d78f 100644 --- a/rust/kernel/ptr.rs +++ b/rust/kernel/ptr.rs @@ -2,7 +2,10 @@ //! Types and functions to work with pointers and addresses. -use core::mem::align_of; +use core::mem::{ + align_of, + size_of, // +}; use core::num::NonZero; /// Type representing an alignment, which is always a power of two. @@ -225,3 +228,25 @@ macro_rules! impl_alignable_uint { } impl_alignable_uint!(u8, u16, u32, u64, usize); + +/// Trait to represent compile-time known size information. +/// +/// This is a generalization of [`size_of`] that works for dynamically sized types. +pub trait KnownSize { + /// Get the size of an object of this type in bytes, with the metadata of the given pointer. + fn size(p: *const Self) -> usize; +} + +impl KnownSize for T { + #[inline(always)] + fn size(_: *const Self) -> usize { + size_of::() + } +} + +impl KnownSize for [T] { + #[inline(always)] + fn size(p: *const Self) -> usize { + p.len() * size_of::() + } +} -- cgit v1.2.3 From f41941aab3acd33f13d65a2ae496329bc8ae4de0 Mon Sep 17 00:00:00 2001 From: Gary Guo Date: Mon, 2 Mar 2026 16:42:35 +0000 Subject: rust: ptr: add projection infrastructure Add a generic infrastructure for performing field and index projections on raw pointers. This will form the basis of performing I/O projections. Pointers manipulations are intentionally using the safe wrapping variants instead of the unsafe variants, as the latter requires pointers to be inside an allocation which is not necessarily true for I/O pointers. This projection macro protects against rogue `Deref` implementation, which can causes the projected pointer to be outside the bounds of starting pointer. This is extremely unlikely and Rust has a lint to catch this, but is unsoundness regardless. The protection works by inducing type inference ambiguity when `Deref` is implemented. This projection macro also stops projecting into unaligned fields (i.e. fields of `#[repr(packed)]` structs), as misaligned pointers require special handling. This is implemented by attempting to create reference to projected field inside a `if false` block. Despite being unreachable, Rust still checks that they're not unaligned fields. The projection macro supports both fallible and infallible index projections. These are described in detail inside the documentation. Signed-off-by: Gary Guo Reviewed-by: Benno Lossin Acked-by: Miguel Ojeda Link: https://patch.msgid.link/20260302164239.284084-3-gary@kernel.org [ * Add intro-doc links where possible, * Fix typos and slightly improve wording, e.g. "as documentation describes" -> "as the documentation of [`Self::proj`] describes", * Add an empty line between regular and safety comments, before examples, and between logically independent comments, * Capitalize various safety comments. - Danilo ] Signed-off-by: Danilo Krummrich --- rust/kernel/lib.rs | 3 + rust/kernel/ptr.rs | 3 + rust/kernel/ptr/projection.rs | 305 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 311 insertions(+) create mode 100644 rust/kernel/ptr/projection.rs (limited to 'rust/kernel') diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 510cc7fe4961..d93292d47420 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -38,6 +38,9 @@ #![feature(const_ptr_write)] #![feature(const_refs_to_cell)] // +// Stable since Rust 1.84.0. +#![feature(strict_provenance)] +// // Expected to become stable. #![feature(arbitrary_self_types)] // diff --git a/rust/kernel/ptr.rs b/rust/kernel/ptr.rs index e91de5f0d78f..bdc2d79ff669 100644 --- a/rust/kernel/ptr.rs +++ b/rust/kernel/ptr.rs @@ -2,6 +2,9 @@ //! Types and functions to work with pointers and addresses. +pub mod projection; +pub use crate::project_pointer as project; + use core::mem::{ align_of, size_of, // diff --git a/rust/kernel/ptr/projection.rs b/rust/kernel/ptr/projection.rs new file mode 100644 index 000000000000..140ea8e21617 --- /dev/null +++ b/rust/kernel/ptr/projection.rs @@ -0,0 +1,305 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Infrastructure for handling projections. + +use core::{ + mem::MaybeUninit, + ops::Deref, // +}; + +use crate::prelude::*; + +/// Error raised when a projection is attempted on an array or slice out of bounds. +pub struct OutOfBound; + +impl From for Error { + #[inline(always)] + fn from(_: OutOfBound) -> Self { + ERANGE + } +} + +/// A helper trait to perform index projection. +/// +/// This is similar to [`core::slice::SliceIndex`], but operates on raw pointers safely and +/// fallibly. +/// +/// # Safety +/// +/// The implementation of `index` and `get` (if [`Some`] is returned) must ensure that, if provided +/// input pointer `slice` and returned pointer `output`, then: +/// - `output` has the same provenance as `slice`; +/// - `output.byte_offset_from(slice)` is between 0 to +/// `KnownSize::size(slice) - KnownSize::size(output)`. +/// +/// This means that if the input pointer is valid, then pointer returned by `get` or `index` is +/// also valid. +#[diagnostic::on_unimplemented(message = "`{Self}` cannot be used to index `{T}`")] +#[doc(hidden)] +pub unsafe trait ProjectIndex: Sized { + type Output: ?Sized; + + /// Returns an index-projected pointer, if in bounds. + fn get(self, slice: *mut T) -> Option<*mut Self::Output>; + + /// Returns an index-projected pointer; fail the build if it cannot be proved to be in bounds. + #[inline(always)] + fn index(self, slice: *mut T) -> *mut Self::Output { + Self::get(self, slice).unwrap_or_else(|| build_error!()) + } +} + +// Forward array impl to slice impl. +// +// SAFETY: Safety requirement guaranteed by the forwarded impl. +unsafe impl ProjectIndex<[T; N]> for I +where + I: ProjectIndex<[T]>, +{ + type Output = >::Output; + + #[inline(always)] + fn get(self, slice: *mut [T; N]) -> Option<*mut Self::Output> { + >::get(self, slice) + } + + #[inline(always)] + fn index(self, slice: *mut [T; N]) -> *mut Self::Output { + >::index(self, slice) + } +} + +// SAFETY: `get`-returned pointer has the same provenance as `slice` and the offset is checked to +// not exceed the required bound. +unsafe impl ProjectIndex<[T]> for usize { + type Output = T; + + #[inline(always)] + fn get(self, slice: *mut [T]) -> Option<*mut T> { + if self >= slice.len() { + None + } else { + Some(slice.cast::().wrapping_add(self)) + } + } +} + +// SAFETY: `get`-returned pointer has the same provenance as `slice` and the offset is checked to +// not exceed the required bound. +unsafe impl ProjectIndex<[T]> for core::ops::Range { + type Output = [T]; + + #[inline(always)] + fn get(self, slice: *mut [T]) -> Option<*mut [T]> { + let new_len = self.end.checked_sub(self.start)?; + if self.end > slice.len() { + return None; + } + Some(core::ptr::slice_from_raw_parts_mut( + slice.cast::().wrapping_add(self.start), + new_len, + )) + } +} + +// SAFETY: Safety requirement guaranteed by the forwarded impl. +unsafe impl ProjectIndex<[T]> for core::ops::RangeTo { + type Output = [T]; + + #[inline(always)] + fn get(self, slice: *mut [T]) -> Option<*mut [T]> { + (0..self.end).get(slice) + } +} + +// SAFETY: Safety requirement guaranteed by the forwarded impl. +unsafe impl ProjectIndex<[T]> for core::ops::RangeFrom { + type Output = [T]; + + #[inline(always)] + fn get(self, slice: *mut [T]) -> Option<*mut [T]> { + (self.start..slice.len()).get(slice) + } +} + +// SAFETY: `get` returned the pointer as is, so it always has the same provenance and offset of 0. +unsafe impl ProjectIndex<[T]> for core::ops::RangeFull { + type Output = [T]; + + #[inline(always)] + fn get(self, slice: *mut [T]) -> Option<*mut [T]> { + Some(slice) + } +} + +/// A helper trait to perform field projection. +/// +/// This trait has a `DEREF` generic parameter so it can be implemented twice for types that +/// implement [`Deref`]. This will cause an ambiguity error and thus block [`Deref`] types being +/// used as base of projection, as they can inject unsoundness. Users therefore must not specify +/// `DEREF` and should always leave it to be inferred. +/// +/// # Safety +/// +/// `proj` may only invoke `f` with a valid allocation, as the documentation of [`Self::proj`] +/// describes. +#[doc(hidden)] +pub unsafe trait ProjectField { + /// Project a pointer to a type to a pointer of a field. + /// + /// `f` may only be invoked with a valid allocation so it can safely obtain raw pointers to + /// fields using `&raw mut`. + /// + /// This is needed because `base` might not point to a valid allocation, while `&raw mut` + /// requires pointers to be in bounds of a valid allocation. + /// + /// # Safety + /// + /// `f` must return a pointer in bounds of the provided pointer. + unsafe fn proj(base: *mut Self, f: impl FnOnce(*mut Self) -> *mut F) -> *mut F; +} + +// NOTE: in theory, this API should work for `T: ?Sized` and `F: ?Sized`, too. However, we cannot +// currently support that as we need to obtain a valid allocation that `&raw const` can operate on. +// +// SAFETY: `proj` invokes `f` with valid allocation. +unsafe impl ProjectField for T { + #[inline(always)] + unsafe fn proj(base: *mut Self, f: impl FnOnce(*mut Self) -> *mut F) -> *mut F { + // Create a valid allocation to start projection, as `base` is not necessarily so. The + // memory is never actually used so it will be optimized out, so it should work even for + // very large `T` (`memoffset` crate also relies on this). To be extra certain, we also + // annotate `f` closure with `#[inline(always)]` in the macro. + let mut place = MaybeUninit::uninit(); + let place_base = place.as_mut_ptr(); + let field = f(place_base); + // SAFETY: `field` is in bounds from `base` per safety requirement. + let offset = unsafe { field.byte_offset_from(place_base) }; + // Use `wrapping_byte_offset` as `base` does not need to be of valid allocation. + base.wrapping_byte_offset(offset).cast() + } +} + +// SAFETY: Vacuously satisfied. +unsafe impl ProjectField for T { + #[inline(always)] + unsafe fn proj(_: *mut Self, _: impl FnOnce(*mut Self) -> *mut F) -> *mut F { + build_error!("this function is a guard against `Deref` impl and is never invoked"); + } +} + +/// Create a projection from a raw pointer. +/// +/// The projected pointer is within the memory region marked by the input pointer. There is no +/// requirement that the input raw pointer needs to be valid, so this macro may be used for +/// projecting pointers outside normal address space, e.g. I/O pointers. However, if the input +/// pointer is valid, the projected pointer is also valid. +/// +/// Supported projections include field projections and index projections. +/// It is not allowed to project into types that implement custom [`Deref`] or +/// [`Index`](core::ops::Index). +/// +/// The macro has basic syntax of `kernel::ptr::project!(ptr, projection)`, where `ptr` is an +/// expression that evaluates to a raw pointer which serves as the base of projection. `projection` +/// can be a projection expression of form `.field` (normally identifier, or numeral in case of +/// tuple structs) or of form `[index]`. +/// +/// If a mutable pointer is needed, the macro input can be prefixed with the `mut` keyword, i.e. +/// `kernel::ptr::project!(mut ptr, projection)`. By default, a const pointer is created. +/// +/// `ptr::project!` macro can perform both fallible indexing and build-time checked indexing. +/// `[index]` form performs build-time bounds checking; if compiler fails to prove `[index]` is in +/// bounds, compilation will fail. `[index]?` can be used to perform runtime bounds checking; +/// `OutOfBound` error is raised via `?` if the index is out of bounds. +/// +/// # Examples +/// +/// Field projections are performed with `.field_name`: +/// +/// ``` +/// struct MyStruct { field: u32, } +/// let ptr: *const MyStruct = core::ptr::dangling(); +/// let field_ptr: *const u32 = kernel::ptr::project!(ptr, .field); +/// +/// struct MyTupleStruct(u32, u32); +/// +/// fn proj(ptr: *const MyTupleStruct) { +/// let field_ptr: *const u32 = kernel::ptr::project!(ptr, .1); +/// } +/// ``` +/// +/// Index projections are performed with `[index]`: +/// +/// ``` +/// fn proj(ptr: *const [u8; 32]) -> Result { +/// let field_ptr: *const u8 = kernel::ptr::project!(ptr, [1]); +/// // The following invocation, if uncommented, would fail the build. +/// // +/// // kernel::ptr::project!(ptr, [128]); +/// +/// // This will raise an `OutOfBound` error (which is convertible to `ERANGE`). +/// kernel::ptr::project!(ptr, [128]?); +/// Ok(()) +/// } +/// ``` +/// +/// If you need to match on the error instead of propagate, put the invocation inside a closure: +/// +/// ``` +/// let ptr: *const [u8; 32] = core::ptr::dangling(); +/// let field_ptr: Result<*const u8> = (|| -> Result<_> { +/// Ok(kernel::ptr::project!(ptr, [128]?)) +/// })(); +/// assert!(field_ptr.is_err()); +/// ``` +/// +/// For mutable pointers, put `mut` as the first token in macro invocation. +/// +/// ``` +/// let ptr: *mut [(u8, u16); 32] = core::ptr::dangling_mut(); +/// let field_ptr: *mut u16 = kernel::ptr::project!(mut ptr, [1].1); +/// ``` +#[macro_export] +macro_rules! project_pointer { + (@gen $ptr:ident, ) => {}; + // Field projection. `$field` needs to be `tt` to support tuple index like `.0`. + (@gen $ptr:ident, .$field:tt $($rest:tt)*) => { + // SAFETY: The provided closure always returns an in-bounds pointer. + let $ptr = unsafe { + $crate::ptr::projection::ProjectField::proj($ptr, #[inline(always)] |ptr| { + // Check unaligned field. Not all users (e.g. DMA) can handle unaligned + // projections. + if false { + let _ = &(*ptr).$field; + } + // SAFETY: `$field` is in bounds, and no implicit `Deref` is possible (if the + // type implements `Deref`, Rust cannot infer the generic parameter `DEREF`). + &raw mut (*ptr).$field + }) + }; + $crate::ptr::project!(@gen $ptr, $($rest)*) + }; + // Fallible index projection. + (@gen $ptr:ident, [$index:expr]? $($rest:tt)*) => { + let $ptr = $crate::ptr::projection::ProjectIndex::get($index, $ptr) + .ok_or($crate::ptr::projection::OutOfBound)?; + $crate::ptr::project!(@gen $ptr, $($rest)*) + }; + // Build-time checked index projection. + (@gen $ptr:ident, [$index:expr] $($rest:tt)*) => { + let $ptr = $crate::ptr::projection::ProjectIndex::index($index, $ptr); + $crate::ptr::project!(@gen $ptr, $($rest)*) + }; + (mut $ptr:expr, $($proj:tt)*) => {{ + let ptr: *mut _ = $ptr; + $crate::ptr::project!(@gen ptr, $($proj)*); + ptr + }}; + ($ptr:expr, $($proj:tt)*) => {{ + let ptr = <*const _>::cast_mut($ptr); + // We currently always project using mutable pointer, as it is not decided whether `&raw + // const` allows the resulting pointer to be mutated (see documentation of `addr_of!`). + $crate::ptr::project!(@gen ptr, $($proj)*); + ptr.cast_const() + }}; +} -- cgit v1.2.3 From 4da879a0d3fd170a70994b73baa554c6913918b5 Mon Sep 17 00:00:00 2001 From: Gary Guo Date: Mon, 2 Mar 2026 16:42:36 +0000 Subject: rust: dma: use pointer projection infra for `dma_{read,write}` macro Current `dma_read!`, `dma_write!` macros also use a custom `addr_of!()`-based implementation for projecting pointers, which has soundness issue as it relies on absence of `Deref` implementation on types. It also has a soundness issue where it does not protect against unaligned fields (when `#[repr(packed)]` is used) so it can generate misaligned accesses. This commit migrates them to use the general pointer projection infrastructure, which handles these cases correctly. As part of migration, the macro is updated to have an improved surface syntax. The current macro have dma_read!(a.b.c[d].e.f) to mean `a.b.c` is a DMA coherent allocation and it should project into it with `[d].e.f` and do a read, which is confusing as it makes the indexing operator integral to the macro (so it will break if you have an array of `CoherentAllocation`, for example). This also is problematic as we would like to generalize `CoherentAllocation` from just slices to arbitrary types. Make the macro expects `dma_read!(path.to.dma, .path.inside.dma)` as the canonical syntax. The index operator is no longer special and is just one type of projection (in additional to field projection). Similarly, make `dma_write!(path.to.dma, .path.inside.dma, value)` become the canonical syntax for writing. Another issue of the current macro is that it is always fallible. This makes sense with existing design of `CoherentAllocation`, but once we support fixed size arrays with `CoherentAllocation`, it is desirable to have the ability to perform infallible indexing as well, e.g. doing a `[0]` index of `[Foo; 2]` is okay and can be checked at build-time, so forcing falliblity is non-ideal. To capture this, the macro is changed to use `[idx]` as infallible projection and `[idx]?` as fallible index projection (those syntax are part of the general projection infra). A benefit of this is that while individual indexing operation may fail, the overall read/write operation is not fallible. Fixes: ad2907b4e308 ("rust: add dma coherent allocator abstraction") Reviewed-by: Benno Lossin Signed-off-by: Gary Guo Link: https://patch.msgid.link/20260302164239.284084-4-gary@kernel.org [ Capitalize safety comments; slightly improve wording in doc-comments. - Danilo ] Signed-off-by: Danilo Krummrich --- rust/kernel/dma.rs | 114 +++++++++++++++++++++++------------------------------ 1 file changed, 50 insertions(+), 64 deletions(-) (limited to 'rust/kernel') diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs index 909d56fd5118..a396f8435739 100644 --- a/rust/kernel/dma.rs +++ b/rust/kernel/dma.rs @@ -461,6 +461,19 @@ impl CoherentAllocation { self.count * core::mem::size_of::() } + /// Returns the raw pointer to the allocated region in the CPU's virtual address space. + #[inline] + pub fn as_ptr(&self) -> *const [T] { + core::ptr::slice_from_raw_parts(self.cpu_addr.as_ptr(), self.count) + } + + /// Returns the raw pointer to the allocated region in the CPU's virtual address space as + /// a mutable pointer. + #[inline] + pub fn as_mut_ptr(&self) -> *mut [T] { + core::ptr::slice_from_raw_parts_mut(self.cpu_addr.as_ptr(), self.count) + } + /// Returns the base address to the allocated region in the CPU's virtual address space. pub fn start_ptr(&self) -> *const T { self.cpu_addr.as_ptr() @@ -581,23 +594,6 @@ impl CoherentAllocation { Ok(()) } - /// Returns a pointer to an element from the region with bounds checking. `offset` is in - /// units of `T`, not the number of bytes. - /// - /// Public but hidden since it should only be used from [`dma_read`] and [`dma_write`] macros. - #[doc(hidden)] - pub fn item_from_index(&self, offset: usize) -> Result<*mut T> { - if offset >= self.count { - return Err(EINVAL); - } - // SAFETY: - // - The pointer is valid due to type invariant on `CoherentAllocation` - // and we've just checked that the range and index is within bounds. - // - `offset` can't overflow since it is smaller than `self.count` and we've checked - // that `self.count` won't overflow early in the constructor. - Ok(unsafe { self.cpu_addr.as_ptr().add(offset) }) - } - /// Reads the value of `field` and ensures that its type is [`FromBytes`]. /// /// # Safety @@ -670,6 +666,9 @@ unsafe impl Send for CoherentAllocation {} /// Reads a field of an item from an allocated region of structs. /// +/// The syntax is of the form `kernel::dma_read!(dma, proj)` where `dma` is an expression evaluating +/// to a [`CoherentAllocation`] and `proj` is a [projection specification](kernel::ptr::project!). +/// /// # Examples /// /// ``` @@ -684,36 +683,29 @@ unsafe impl Send for CoherentAllocation {} /// unsafe impl kernel::transmute::AsBytes for MyStruct{}; /// /// # fn test(alloc: &kernel::dma::CoherentAllocation) -> Result { -/// let whole = kernel::dma_read!(alloc[2]); -/// let field = kernel::dma_read!(alloc[1].field); +/// let whole = kernel::dma_read!(alloc, [2]?); +/// let field = kernel::dma_read!(alloc, [1]?.field); /// # Ok::<(), Error>(()) } /// ``` #[macro_export] macro_rules! dma_read { - ($dma:expr, $idx: expr, $($field:tt)*) => {{ - (|| -> ::core::result::Result<_, $crate::error::Error> { - let item = $crate::dma::CoherentAllocation::item_from_index(&$dma, $idx)?; - // SAFETY: `item_from_index` ensures that `item` is always a valid pointer and can be - // dereferenced. The compiler also further validates the expression on whether `field` - // is a member of `item` when expanded by the macro. - unsafe { - let ptr_field = ::core::ptr::addr_of!((*item) $($field)*); - ::core::result::Result::Ok( - $crate::dma::CoherentAllocation::field_read(&$dma, ptr_field) - ) - } - })() + ($dma:expr, $($proj:tt)*) => {{ + let dma = &$dma; + let ptr = $crate::ptr::project!( + $crate::dma::CoherentAllocation::as_ptr(dma), $($proj)* + ); + // SAFETY: The pointer created by the projection is within the DMA region. + unsafe { $crate::dma::CoherentAllocation::field_read(dma, ptr) } }}; - ($dma:ident [ $idx:expr ] $($field:tt)* ) => { - $crate::dma_read!($dma, $idx, $($field)*) - }; - ($($dma:ident).* [ $idx:expr ] $($field:tt)* ) => { - $crate::dma_read!($($dma).*, $idx, $($field)*) - }; } /// Writes to a field of an item from an allocated region of structs. /// +/// The syntax is of the form `kernel::dma_write!(dma, proj, val)` where `dma` is an expression +/// evaluating to a [`CoherentAllocation`], `proj` is a +/// [projection specification](kernel::ptr::project!), and `val` is the value to be written to the +/// projected location. +/// /// # Examples /// /// ``` @@ -728,37 +720,31 @@ macro_rules! dma_read { /// unsafe impl kernel::transmute::AsBytes for MyStruct{}; /// /// # fn test(alloc: &kernel::dma::CoherentAllocation) -> Result { -/// kernel::dma_write!(alloc[2].member = 0xf); -/// kernel::dma_write!(alloc[1] = MyStruct { member: 0xf }); +/// kernel::dma_write!(alloc, [2]?.member, 0xf); +/// kernel::dma_write!(alloc, [1]?, MyStruct { member: 0xf }); /// # Ok::<(), Error>(()) } /// ``` #[macro_export] macro_rules! dma_write { - ($dma:ident [ $idx:expr ] $($field:tt)*) => {{ - $crate::dma_write!($dma, $idx, $($field)*) - }}; - ($($dma:ident).* [ $idx:expr ] $($field:tt)* ) => {{ - $crate::dma_write!($($dma).*, $idx, $($field)*) + (@parse [$dma:expr] [$($proj:tt)*] [, $val:expr]) => {{ + let dma = &$dma; + let ptr = $crate::ptr::project!( + mut $crate::dma::CoherentAllocation::as_mut_ptr(dma), $($proj)* + ); + let val = $val; + // SAFETY: The pointer created by the projection is within the DMA region. + unsafe { $crate::dma::CoherentAllocation::field_write(dma, ptr, val) } }}; - ($dma:expr, $idx: expr, = $val:expr) => { - (|| -> ::core::result::Result<_, $crate::error::Error> { - let item = $crate::dma::CoherentAllocation::item_from_index(&$dma, $idx)?; - // SAFETY: `item_from_index` ensures that `item` is always a valid item. - unsafe { $crate::dma::CoherentAllocation::field_write(&$dma, item, $val) } - ::core::result::Result::Ok(()) - })() + (@parse [$dma:expr] [$($proj:tt)*] [.$field:tt $($rest:tt)*]) => { + $crate::dma_write!(@parse [$dma] [$($proj)* .$field] [$($rest)*]) + }; + (@parse [$dma:expr] [$($proj:tt)*] [[$index:expr]? $($rest:tt)*]) => { + $crate::dma_write!(@parse [$dma] [$($proj)* [$index]?] [$($rest)*]) + }; + (@parse [$dma:expr] [$($proj:tt)*] [[$index:expr] $($rest:tt)*]) => { + $crate::dma_write!(@parse [$dma] [$($proj)* [$index]] [$($rest)*]) }; - ($dma:expr, $idx: expr, $(.$field:ident)* = $val:expr) => { - (|| -> ::core::result::Result<_, $crate::error::Error> { - let item = $crate::dma::CoherentAllocation::item_from_index(&$dma, $idx)?; - // SAFETY: `item_from_index` ensures that `item` is always a valid pointer and can be - // dereferenced. The compiler also further validates the expression on whether `field` - // is a member of `item` when expanded by the macro. - unsafe { - let ptr_field = ::core::ptr::addr_of_mut!((*item) $(.$field)*); - $crate::dma::CoherentAllocation::field_write(&$dma, ptr_field, $val) - } - ::core::result::Result::Ok(()) - })() + ($dma:expr, $($rest:tt)*) => { + $crate::dma_write!(@parse [$dma] [] [$($rest)*]) }; } -- cgit v1.2.3 From 487f9b3dc6e507a982f1b984aa6bfbd9dc4b0567 Mon Sep 17 00:00:00 2001 From: John Hubbard Date: Wed, 11 Mar 2026 21:19:34 -0700 Subject: rust: cpufreq: suppress clippy::double_parens in Policy doctest The kernel fmt! proc macro wraps each format argument as &(arg). Passing a tuple such as (a, b) produces &((a, b)) after expansion. Clippy flags that as double_parens, but it is a false positive fixed in Clippy 1.92 [1] [2]. Suppress the warning on the affected doctest function with a reason attribute so it can be removed once the minimum toolchain moves past 1.92. [ We may end up deciding to support per-version Clippy lints, in which case we will need [3]. In the future, if [4] gets fixed, we may be able to use `Delimiter::None` as Gary suggested in [5]. Link: https://lore.kernel.org/rust-for-linux/20260307170929.153892-1-ojeda@kernel.org/ [3] Link: https://github.com/rust-lang/rust/issues/67062 [4] Link: https://lore.kernel.org/rust-for-linux/DGUA5GY2DGYN.3PG0FKLG7GFN1@garyguo.net/ [5] - Miguel ] Link: https://github.com/rust-lang/rust-clippy/issues/15852 [1] Link: https://github.com/rust-lang/rust-clippy/pull/15939 [2] Suggested-by: Gary Guo Signed-off-by: John Hubbard Acked-by: Viresh Kumar Link: https://patch.msgid.link/20260312041934.362840-2-jhubbard@nvidia.com [ Reworded to replace GitHub-like short link with full URLs in Link tags. Reworded reason string to match the style of a couple others we have elsewhere. - Miguel ] Signed-off-by: Miguel Ojeda --- rust/kernel/cpufreq.rs | 1 + 1 file changed, 1 insertion(+) (limited to 'rust/kernel') diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs index 76faa1ac8501..f5adee48d40c 100644 --- a/rust/kernel/cpufreq.rs +++ b/rust/kernel/cpufreq.rs @@ -401,6 +401,7 @@ impl TableBuilder { /// ``` /// use kernel::cpufreq::{DEFAULT_TRANSITION_LATENCY_NS, Policy}; /// +/// #[allow(clippy::double_parens, reason = "False positive before 1.92.0")] /// fn update_policy(policy: &mut Policy) { /// policy /// .set_dvfs_possible_from_any_cpu(true) -- cgit v1.2.3 From c51866f65b8ac37b8883a2e80ada13c8cd4d2f7b Mon Sep 17 00:00:00 2001 From: Lyude Paul Date: Fri, 14 Nov 2025 13:42:06 -0500 Subject: rust/time: Add Delta::from_nanos() Since rvkms is going to need to create its own Delta instances, and we already have functions for creating Delta with every other unit of time. Signed-off-by: Lyude Paul Reviewed-by: Alice Ryhl Link: https://msgid.link/20251114184207.459335-1-lyude@redhat.com Signed-off-by: Andreas Hindborg --- rust/kernel/time.rs | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'rust/kernel') diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs index 6ea98dfcd027..2b096e5a61cd 100644 --- a/rust/kernel/time.rs +++ b/rust/kernel/time.rs @@ -363,6 +363,12 @@ impl Delta { /// A span of time equal to zero. pub const ZERO: Self = Self { nanos: 0 }; + /// Create a new [`Delta`] from a number of nanoseconds. + #[inline] + pub const fn from_nanos(nanos: i64) -> Self { + Self { nanos } + } + /// Create a new [`Delta`] from a number of microseconds. /// /// The `micros` can range from -9_223_372_036_854_775 to 9_223_372_036_854_775. -- cgit v1.2.3 From 67b598db7ef107d80091c4c957694b9a2feffa4c Mon Sep 17 00:00:00 2001 From: FUJITA Tomonori Date: Mon, 30 Jun 2025 22:10:11 +0900 Subject: rust: time: make ClockSource unsafe trait Mark the ClockSource trait as unsafe and document its safety requirements. Specifically, implementers must guarantee that their `ktime_get()` implementation returns a value in the inclusive range [0, KTIME_MAX]. Update all existing implementations to use `unsafe impl` with corresponding safety comments. Note that there could be potential users of a customized clock source [1] so we don't seal the trait. Link: https://lore.kernel.org/rust-for-linux/Z9xb1r1x5tOzAIZT@boqun-archlinux/ [1] Suggested-by: Boqun Feng Signed-off-by: FUJITA Tomonori Reviewed-by: Alice Ryhl Link: https://msgid.link/20250630131011.405219-1-fujita.tomonori@gmail.com [ Change range expressions in docs. - Andreas ] Signed-off-by: Andreas Hindborg --- rust/kernel/time.rs | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) (limited to 'rust/kernel') diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs index 2b096e5a61cd..363e93cbb139 100644 --- a/rust/kernel/time.rs +++ b/rust/kernel/time.rs @@ -60,7 +60,13 @@ pub fn msecs_to_jiffies(msecs: Msecs) -> Jiffies { /// cases the user of the clock has to decide which clock is best suited for the /// purpose. In most scenarios clock [`Monotonic`] is the best choice as it /// provides a accurate monotonic notion of time (leap second smearing ignored). -pub trait ClockSource { +/// +/// # Safety +/// +/// Implementers must ensure that `ktime_get()` returns a value in the inclusive range +/// `0..=KTIME_MAX` (i.e., greater than or equal to 0 and less than or equal to +/// `KTIME_MAX`, where `KTIME_MAX` equals `i64::MAX`). +pub unsafe trait ClockSource { /// The kernel clock ID associated with this clock source. /// /// This constant corresponds to the C side `clockid_t` value. @@ -68,7 +74,7 @@ pub trait ClockSource { /// Get the current time from the clock source. /// - /// The function must return a value in the range from 0 to `KTIME_MAX`. + /// The function must return a value in the range `0..=KTIME_MAX`. fn ktime_get() -> bindings::ktime_t; } @@ -85,7 +91,9 @@ pub trait ClockSource { /// count time that the system is suspended. pub struct Monotonic; -impl ClockSource for Monotonic { +// SAFETY: The kernel's `ktime_get()` is guaranteed to return a value +// in `0..=KTIME_MAX`. +unsafe impl ClockSource for Monotonic { const ID: bindings::clockid_t = bindings::CLOCK_MONOTONIC as bindings::clockid_t; fn ktime_get() -> bindings::ktime_t { @@ -110,7 +118,9 @@ impl ClockSource for Monotonic { /// the clock will experience discontinuity around leap second adjustment. pub struct RealTime; -impl ClockSource for RealTime { +// SAFETY: The kernel's `ktime_get_real()` is guaranteed to return a value +// in `0..=KTIME_MAX`. +unsafe impl ClockSource for RealTime { const ID: bindings::clockid_t = bindings::CLOCK_REALTIME as bindings::clockid_t; fn ktime_get() -> bindings::ktime_t { @@ -128,7 +138,9 @@ impl ClockSource for RealTime { /// discontinuities if the time is changed using settimeofday(2) or similar. pub struct BootTime; -impl ClockSource for BootTime { +// SAFETY: The kernel's `ktime_get_boottime()` is guaranteed to return a value +// in `0..=KTIME_MAX`. +unsafe impl ClockSource for BootTime { const ID: bindings::clockid_t = bindings::CLOCK_BOOTTIME as bindings::clockid_t; fn ktime_get() -> bindings::ktime_t { @@ -150,7 +162,9 @@ impl ClockSource for BootTime { /// The acronym TAI refers to International Atomic Time. pub struct Tai; -impl ClockSource for Tai { +// SAFETY: The kernel's `ktime_get_clocktai()` is guaranteed to return a value +// in `0..=KTIME_MAX`. +unsafe impl ClockSource for Tai { const ID: bindings::clockid_t = bindings::CLOCK_TAI as bindings::clockid_t; fn ktime_get() -> bindings::ktime_t { -- cgit v1.2.3 From ddb1444d3335129ae87d9796ab1debf41c0ee51b Mon Sep 17 00:00:00 2001 From: Andreas Hindborg Date: Thu, 19 Feb 2026 12:57:45 +0100 Subject: hrtimer: add usage examples to documentation Add documentation examples showing various ways to use hrtimers: - Box-allocated timers with shared state in Arc. - Arc-allocated timers. - Stack-based timers for scoped usage. - Mutable stack-based timers with shared state. Tested-by: Daniel Almeida Reviewed-by: Daniel Almeida Reviewed-by: Alice Ryhl Link: https://msgid.link/20260219-hrtimer-examples-v6-19-rc1-v2-1-810cc06ca9f6@kernel.org Signed-off-by: Andreas Hindborg --- rust/kernel/time/hrtimer.rs | 336 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 336 insertions(+) (limited to 'rust/kernel') diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs index 856d2d929a00..2d7f1131a813 100644 --- a/rust/kernel/time/hrtimer.rs +++ b/rust/kernel/time/hrtimer.rs @@ -66,6 +66,342 @@ //! //! A `restart` operation on a timer in the **stopped** state is equivalent to a //! `start` operation. +//! +//! When a type implements both `HrTimerPointer` and `Clone`, it is possible to +//! issue the `start` operation while the timer is in the **started** state. In +//! this case the `start` operation is equivalent to the `restart` operation. +//! +//! # Examples +//! +//! ## Using an intrusive timer living in a [`Box`] +//! +//! ``` +//! # use kernel::{ +//! # alloc::flags, +//! # impl_has_hr_timer, +//! # prelude::*, +//! # sync::{ +//! # atomic::{ordering, Atomic}, +//! # completion::Completion, +//! # Arc, +//! # }, +//! # time::{ +//! # hrtimer::{ +//! # RelativeMode, HrTimer, HrTimerCallback, HrTimerPointer, +//! # HrTimerRestart, HrTimerCallbackContext +//! # }, +//! # Delta, Monotonic, +//! # }, +//! # }; +//! +//! #[pin_data] +//! struct Shared { +//! #[pin] +//! flag: Atomic, +//! #[pin] +//! cond: Completion, +//! } +//! +//! impl Shared { +//! fn new() -> impl PinInit { +//! pin_init!(Self { +//! flag <- Atomic::new(0), +//! cond <- Completion::new(), +//! }) +//! } +//! } +//! +//! #[pin_data] +//! struct BoxIntrusiveHrTimer { +//! #[pin] +//! timer: HrTimer, +//! shared: Arc, +//! } +//! +//! impl BoxIntrusiveHrTimer { +//! fn new() -> impl PinInit { +//! try_pin_init!(Self { +//! timer <- HrTimer::new(), +//! shared: Arc::pin_init(Shared::new(), flags::GFP_KERNEL)?, +//! }) +//! } +//! } +//! +//! impl HrTimerCallback for BoxIntrusiveHrTimer { +//! type Pointer<'a> = Pin>; +//! +//! fn run(this: Pin<&mut Self>, _ctx: HrTimerCallbackContext<'_, Self>) -> HrTimerRestart { +//! pr_info!("Timer called\n"); +//! +//! let flag = this.shared.flag.fetch_add(1, ordering::Full); +//! this.shared.cond.complete_all(); +//! +//! if flag == 4 { +//! HrTimerRestart::NoRestart +//! } else { +//! HrTimerRestart::Restart +//! } +//! } +//! } +//! +//! impl_has_hr_timer! { +//! impl HasHrTimer for BoxIntrusiveHrTimer { +//! mode: RelativeMode, field: self.timer +//! } +//! } +//! +//! let has_timer = Box::pin_init(BoxIntrusiveHrTimer::new(), GFP_KERNEL)?; +//! let shared = has_timer.shared.clone(); +//! let _handle = has_timer.start(Delta::from_micros(200)); +//! +//! while shared.flag.load(ordering::Relaxed) != 5 { +//! shared.cond.wait_for_completion(); +//! } +//! +//! pr_info!("Counted to 5\n"); +//! # Ok::<(), kernel::error::Error>(()) +//! ``` +//! +//! ## Using an intrusive timer in an [`Arc`] +//! +//! ``` +//! # use kernel::{ +//! # alloc::flags, +//! # impl_has_hr_timer, +//! # prelude::*, +//! # sync::{ +//! # atomic::{ordering, Atomic}, +//! # completion::Completion, +//! # Arc, ArcBorrow, +//! # }, +//! # time::{ +//! # hrtimer::{ +//! # RelativeMode, HrTimer, HrTimerCallback, HrTimerPointer, HrTimerRestart, +//! # HasHrTimer, HrTimerCallbackContext +//! # }, +//! # Delta, Monotonic, +//! # }, +//! # }; +//! +//! #[pin_data] +//! struct ArcIntrusiveHrTimer { +//! #[pin] +//! timer: HrTimer, +//! #[pin] +//! flag: Atomic, +//! #[pin] +//! cond: Completion, +//! } +//! +//! impl ArcIntrusiveHrTimer { +//! fn new() -> impl PinInit { +//! pin_init!(Self { +//! timer <- HrTimer::new(), +//! flag <- Atomic::new(0), +//! cond <- Completion::new(), +//! }) +//! } +//! } +//! +//! impl HrTimerCallback for ArcIntrusiveHrTimer { +//! type Pointer<'a> = Arc; +//! +//! fn run( +//! this: ArcBorrow<'_, Self>, +//! _ctx: HrTimerCallbackContext<'_, Self>, +//! ) -> HrTimerRestart { +//! pr_info!("Timer called\n"); +//! +//! let flag = this.flag.fetch_add(1, ordering::Full); +//! this.cond.complete_all(); +//! +//! if flag == 4 { +//! HrTimerRestart::NoRestart +//! } else { +//! HrTimerRestart::Restart +//! } +//! } +//! } +//! +//! impl_has_hr_timer! { +//! impl HasHrTimer for ArcIntrusiveHrTimer { +//! mode: RelativeMode, field: self.timer +//! } +//! } +//! +//! let has_timer = Arc::pin_init(ArcIntrusiveHrTimer::new(), GFP_KERNEL)?; +//! let _handle = has_timer.clone().start(Delta::from_micros(200)); +//! +//! while has_timer.flag.load(ordering::Relaxed) != 5 { +//! has_timer.cond.wait_for_completion(); +//! } +//! +//! pr_info!("Counted to 5\n"); +//! # Ok::<(), kernel::error::Error>(()) +//! ``` +//! +//! ## Using a stack-based timer +//! +//! ``` +//! # use kernel::{ +//! # impl_has_hr_timer, +//! # prelude::*, +//! # sync::{ +//! # atomic::{ordering, Atomic}, +//! # completion::Completion, +//! # }, +//! # time::{ +//! # hrtimer::{ +//! # ScopedHrTimerPointer, HrTimer, HrTimerCallback, HrTimerPointer, HrTimerRestart, +//! # HasHrTimer, RelativeMode, HrTimerCallbackContext +//! # }, +//! # Delta, Monotonic, +//! # }, +//! # }; +//! # use pin_init::stack_pin_init; +//! +//! #[pin_data] +//! struct IntrusiveHrTimer { +//! #[pin] +//! timer: HrTimer, +//! #[pin] +//! flag: Atomic, +//! #[pin] +//! cond: Completion, +//! } +//! +//! impl IntrusiveHrTimer { +//! fn new() -> impl PinInit { +//! pin_init!(Self { +//! timer <- HrTimer::new(), +//! flag <- Atomic::new(0), +//! cond <- Completion::new(), +//! }) +//! } +//! } +//! +//! impl HrTimerCallback for IntrusiveHrTimer { +//! type Pointer<'a> = Pin<&'a Self>; +//! +//! fn run(this: Pin<&Self>, _ctx: HrTimerCallbackContext<'_, Self>) -> HrTimerRestart { +//! pr_info!("Timer called\n"); +//! +//! this.flag.store(1, ordering::Release); +//! this.cond.complete_all(); +//! +//! HrTimerRestart::NoRestart +//! } +//! } +//! +//! impl_has_hr_timer! { +//! impl HasHrTimer for IntrusiveHrTimer { +//! mode: RelativeMode, field: self.timer +//! } +//! } +//! +//! stack_pin_init!( let has_timer = IntrusiveHrTimer::new() ); +//! has_timer.as_ref().start_scoped(Delta::from_micros(200), || { +//! while has_timer.flag.load(ordering::Relaxed) != 1 { +//! has_timer.cond.wait_for_completion(); +//! } +//! }); +//! +//! pr_info!("Flag raised\n"); +//! # Ok::<(), kernel::error::Error>(()) +//! ``` +//! +//! ## Using a mutable stack-based timer +//! +//! ``` +//! # use kernel::{ +//! # alloc::flags, +//! # impl_has_hr_timer, +//! # prelude::*, +//! # sync::{ +//! # atomic::{ordering, Atomic}, +//! # completion::Completion, +//! # Arc, +//! # }, +//! # time::{ +//! # hrtimer::{ +//! # ScopedHrTimerPointer, HrTimer, HrTimerCallback, HrTimerPointer, HrTimerRestart, +//! # HasHrTimer, RelativeMode, HrTimerCallbackContext +//! # }, +//! # Delta, Monotonic, +//! # }, +//! # }; +//! # use pin_init::stack_try_pin_init; +//! +//! #[pin_data] +//! struct Shared { +//! #[pin] +//! flag: Atomic, +//! #[pin] +//! cond: Completion, +//! } +//! +//! impl Shared { +//! fn new() -> impl PinInit { +//! pin_init!(Self { +//! flag <- Atomic::new(0), +//! cond <- Completion::new(), +//! }) +//! } +//! } +//! +//! #[pin_data] +//! struct IntrusiveHrTimer { +//! #[pin] +//! timer: HrTimer, +//! shared: Arc, +//! } +//! +//! impl IntrusiveHrTimer { +//! fn new() -> impl PinInit { +//! try_pin_init!(Self { +//! timer <- HrTimer::new(), +//! shared: Arc::pin_init(Shared::new(), flags::GFP_KERNEL)?, +//! }) +//! } +//! } +//! +//! impl HrTimerCallback for IntrusiveHrTimer { +//! type Pointer<'a> = Pin<&'a mut Self>; +//! +//! fn run(this: Pin<&mut Self>, _ctx: HrTimerCallbackContext<'_, Self>) -> HrTimerRestart { +//! pr_info!("Timer called\n"); +//! +//! let flag = this.shared.flag.fetch_add(1, ordering::Full); +//! this.shared.cond.complete_all(); +//! +//! if flag == 4 { +//! HrTimerRestart::NoRestart +//! } else { +//! HrTimerRestart::Restart +//! } +//! } +//! } +//! +//! impl_has_hr_timer! { +//! impl HasHrTimer for IntrusiveHrTimer { +//! mode: RelativeMode, field: self.timer +//! } +//! } +//! +//! stack_try_pin_init!( let has_timer =? IntrusiveHrTimer::new() ); +//! let shared = has_timer.shared.clone(); +//! +//! has_timer.as_mut().start_scoped(Delta::from_micros(200), || { +//! while shared.flag.load(ordering::Relaxed) != 5 { +//! shared.cond.wait_for_completion(); +//! } +//! }); +//! +//! pr_info!("Counted to 5\n"); +//! # Ok::<(), kernel::error::Error>(()) +//! ``` +//! +//! [`Arc`]: kernel::sync::Arc use super::{ClockSource, Delta, Instant}; use crate::{prelude::*, types::Opaque}; -- cgit v1.2.3